1. Field of the Invention
The present invention relates to sensors to detect and map various stimuli spatially distributed over the area of contact with the surface of the sensor. More specifically, the present invention relates to a family of opto-electronic and electronic sensors that by touch or on physical contact with the surface of a body detects features, such as texture and roughness of the body's surface, variation in hardness of a body, palpable structure, shape of a solid object, static-charge on the surface of a body, and temperature distribution of a solid surface. This invention is a family of devices in a form of a thin-film that utilizes nanoparticles and polymers to convert the stimuli on touch over the area of contact to an electrical, or optical, or a combination of electrical and optical signals that can be processed using standard electronics to detect the distribution of the magnitude of the stimuli received over the area of contact. The abovementioned device can substitute for or act in conjunction with one or more human senses.
2. Description of Related Art
Broadly, the sensation of touch is the determination of distribution of physical properties such as, texture, roughness, hardness, static-charge, and temperature over the area of physical contact. The primary function of sense of touch is the determination of the magnitude of stress or pressure distribution over the area of physical contact between the sensor and the object surfaces to “feel” the texture, roughness, hardness and palpable features imbedded in the object tactile or touch sensors of substantial active area of contact is a critical component to advance noninvasive surgical procedures by giving a surgeon the “touch sensation”, for example to determine various normal and diseased tissues of a patient. More specifically, tactile devices are used as medical devices to image the palpable structure in a breast to determine cancerous mass or tumor. It is also a critical component in the development of humanoid robots that can sense shapes, textures, hardness, and manipulate complex objects, which are not possible by vision alone. Touch (or tactile) sensors are usually made as a micro-electromechanical system composed of micro-machined deformable components or by integrating strain sensitive materials, such as magneto-resistive ceramics, piezoelectric polymers, and strain sensitive conducting elastomers. Tactile sensors based on change in the capacitance between two electrodes spaced by a polymer have also been designed using an array of such capacitors. Tactile sensors from optical data have been demonstrated where the contact stress distribution is calculated from the change in shape of the deformable sensor surface obtained by a camera. For small area devices, such as an array of capacitance sensors on an 8 by 8 matrix, a spatial resolution of 100 micrometers (μm) has been demonstrated. However, for a large area device of active (i.e., sensing) area of about 1 cm2 or larger, the spatial resolution for stress distribution is at best in the approximately 2 mm range, which compares poorly with the approximately 40 μm resolution achieved by the human finger.
Thus, there exists a need in the art for improved sensors to replace, complement, or augment one or more human senses of touch. Included among these are touch sensors to sense texture, imbedded palpable features, static charge and spatial variation of temperature. These devices find use in many fields, including the medical field, the sports and health fields, and robotics.